RE: [Xen-devel] HVM kernbench performance on Linux (2.6.27-rc4 vs.2.6.18.6-amd64)

["Ian Pratt" <Ian.Pratt@xxxxxxxxxxxxx>]

> So it seems the problem doesn't occur for me on Debian 4.0 HVM guest,
> as suggested by Gianluca Guida.
> 
> The Debian 4.0 vanilla install has a  2.6.18.6-amd64 kernel.
> 
> The results are below. So it seems that the guest kernel makes a big
> difference.

It sounds like the "find writeable mappings" heuristic might be broken
for newer linux 64b kernels. That will be painful for shadow2, but
catastrophic for shadow3.

I wonder if there's a second 1:1 direct mapping added, or whether the
direct mapping has moved?

Ian


 
> The performance problem is not seen on the debian kernel.
> 
> HVM guest (Debian 4.0 vanilla 2.6.18.6-amd64)
> 
> shadow2
> 2.6.18.6-amd64 guest kernel
> Average Optimal load -j 4 Run (std deviation):
> Elapsed Time 506.658 (4.13104)
> User Time 364.536 (0.337757)
> System Time 140.834 (4.04617)
> Percent CPU 99 (0)
> Context Switches 29803 (120.69)
> Sleeps 37929.2 (355.421)
> 
> shadow3
> 2.6.18.6-amd64 guest kernel
> Average Optimal load -j 4 Run (std deviation):
> Elapsed Time 489.58 (4.00024)
> User Time 389.328 (0.614304)
> System Time 98.838 (4.86796)
> Percent CPU 99 (0)
> Context Switches 29314.6 (196.596)
> Sleeps 37773.6 (231.069)
> 
> vs. the same machine and guest config with a 2.6.27-rc4 guest kernel
> 
> 
> shadow2
> 2.6.27-rc4 guest kernel
> Average Optimal load -j 4 Run (std deviation):
> Elapsed Time 737.144 (5.19414)
> User Time 498.508 (2.52895)
> System Time 235.056 (2.71348)
> Percent CPU 99 (0)
> Context Switches 133127 (823.517)
> Sleeps 36295.4 (124.088)
> 
> 
> shadow 3
> 2.6.27-rc4 guest kernel
> Average Optimal load -j 4 Run (std deviation):
> Elapsed Time 2081.71 (34.0459)
> User Time 617.36 (3.61771)
> System Time 1430.36 (28.3309)
> Percent CPU 98 (0)
> Context Switches 331843 (5283.28)
> Sleeps 37329.8 (91.538)
> 
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